[v3] linux-user: Improve host and guest page size handling

[PATCH v3 02/33] linux-user: Adjust SVr4 NULL page mapping

Posted by Richard Henderson 10 months, 4 weeks ago

Use TARGET_PAGE_SIZE and MAP_FIXED_NOREPLACE.

We really should be attending to this earlier during
probe_guest_base, as well as better detection and
emulation of various Linux personalities.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 linux-user/elfload.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/linux-user/elfload.c b/linux-user/elfload.c
index cf9e74468b..f3c1e0fb64 100644
--- a/linux-user/elfload.c
+++ b/linux-user/elfload.c
@@ -3911,8 +3911,9 @@ int load_elf_binary(struct linux_binprm *bprm, struct image_info *info)
                and some applications "depend" upon this behavior.  Since
                we do not have the power to recompile these, we emulate
                the SVr4 behavior.  Sigh.  */
-            target_mmap(0, qemu_host_page_size, PROT_READ | PROT_EXEC,
-                        MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+            target_mmap(0, TARGET_PAGE_SIZE, PROT_READ | PROT_EXEC,
+                        MAP_FIXED_NOREPLACE | MAP_PRIVATE | MAP_ANONYMOUS,
+                        -1, 0);
         }
 #ifdef TARGET_MIPS
         info->interp_fp_abi = interp_info.fp_abi;
-- 
2.34.1

Re: [PATCH v3 02/33] linux-user: Adjust SVr4 NULL page mapping

Posted by Ilya Leoshkevich 10 months ago

On Tue, Jan 02, 2024 at 12:57:37PM +1100, Richard Henderson wrote:
> Use TARGET_PAGE_SIZE and MAP_FIXED_NOREPLACE.
> 
> We really should be attending to this earlier during
> probe_guest_base, as well as better detection and
> emulation of various Linux personalities.
> 
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>  linux-user/elfload.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/linux-user/elfload.c b/linux-user/elfload.c
> index cf9e74468b..f3c1e0fb64 100644
> --- a/linux-user/elfload.c
> +++ b/linux-user/elfload.c
> @@ -3911,8 +3911,9 @@ int load_elf_binary(struct linux_binprm *bprm, struct image_info *info)
>                 and some applications "depend" upon this behavior.  Since
>                 we do not have the power to recompile these, we emulate
>                 the SVr4 behavior.  Sigh.  */
> -            target_mmap(0, qemu_host_page_size, PROT_READ | PROT_EXEC,
> -                        MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
> +            target_mmap(0, TARGET_PAGE_SIZE, PROT_READ | PROT_EXEC,
> +                        MAP_FIXED_NOREPLACE | MAP_PRIVATE | MAP_ANONYMOUS,
> +                        -1, 0);
>          }
>  #ifdef TARGET_MIPS
>          info->interp_fp_abi = interp_info.fp_abi;
> -- 
> 2.34.1

Nit: should we print a warning if we get EEXIST?

Reviewed-by: Ilya Leoshkevich <iii@linux.ibm.com>

Re: [PATCH v3 02/33] linux-user: Adjust SVr4 NULL page mapping

Posted by Pierrick Bouvier 10 months, 3 weeks ago

On 1/2/24 05:57, Richard Henderson wrote:
> Use TARGET_PAGE_SIZE and MAP_FIXED_NOREPLACE.
> 
> We really should be attending to this earlier during
> probe_guest_base, as well as better detection and
> emulation of various Linux personalities.
> 
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>   linux-user/elfload.c | 5 +++--
>   1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/linux-user/elfload.c b/linux-user/elfload.c
> index cf9e74468b..f3c1e0fb64 100644
> --- a/linux-user/elfload.c
> +++ b/linux-user/elfload.c
> @@ -3911,8 +3911,9 @@ int load_elf_binary(struct linux_binprm *bprm, struct image_info *info)
>                  and some applications "depend" upon this behavior.  Since
>                  we do not have the power to recompile these, we emulate
>                  the SVr4 behavior.  Sigh.  */
> -            target_mmap(0, qemu_host_page_size, PROT_READ | PROT_EXEC,
> -                        MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
> +            target_mmap(0, TARGET_PAGE_SIZE, PROT_READ | PROT_EXEC,
> +                        MAP_FIXED_NOREPLACE | MAP_PRIVATE | MAP_ANONYMOUS,
> +                        -1, 0);
>           }
>   #ifdef TARGET_MIPS
>           info->interp_fp_abi = interp_info.fp_abi;

Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>